Such cushions or mattresses are in fact known, of which certain, and the present invention concerns this category, are made of supple cellular material, namely essentially open-cell foam of polyurethane type, and having a particular form, which makes it possible, on the one hand, to distribute the bearing pressure of the body that they receive, uniformly, in order to avoid points of contact more stressed than others, and on which bedsores might develop, and, on the other hand, to allow slight displacements by lateral deformation, without generating friction.
To that end, such a form which has been commonly used for a long time is of waffle-iron type, comprising a continuous sole, from which projections in the form of frustums of pyramid are distributed uniformly over the whole bearing surface desired.
Different standards exist in certain countries, to define the mininum characteristics of such cushions or mattresses, such as the French standard drawn up by the General Direction of Health, with, in particular, a minimum thickness of 17 cm, of which at least 8 for the sole, a foam density included between 24 and 45 kg/m.sup.3, a remanent deformation less than 10% in accordance with standard ISO 1856, technical qualities of elasticity, of crush resistance and of long-life at least identical to those obtained with high-resilience foams, a fire-resistance in accordance with standard NF P926501, a tear strength greater than 170 N/m in accordance with standard NF T56109.
To satisfy these standards which, moreover, evolve and become increasingly severe, or to propose cushions possibly non-standard but with additional characteristics, various manufacturers have developed:
either various components to obtain a foam corresponding to the above characteristics, or various types of water-proof protections, essentially by removable cover or projection of paint added after the foam has been manufactured; PA1 various processes for employing the foam to obtain the waffle-iron effect by cutting out a block or by pre-moulding same; PA1 or combinations of said foam with other materials and/or other complementary devices. PA1 either by immersion of the mattress or cushion elements in baths such as natural rubber but requiring handlings, manipulations and thickness checks, which increases the cost of the finished product; PA1 or by projection of paint, but, in that case, it is on the one hand impossible to protect the hollow parts which are most exposed to tear and of difficult access for cleaning, and, on the other hand, by manual methods, the projected layer cannot be uniform, which, in the event of excess thickness, modifies the desired surface suppleness, and, if the thickness is too little, does not give sufficient protection, and in any case creates zones of different, therefore unaesthetic, colours. PA1 to automatize this manufacture in complete safety, respecting the regulations concerning the components for making said foam; PA1 to obtain characteristics of said foam which are, on the one hand, in accordance with the standards and, on the other hand, optimum for maximum comfort and of constant and repetitive quality; PA1 to ensure a high manufacturing rate, with a minimum of moulds; PA1 to project a water-proof paint, ensuring a minimum effective protection of the cushion or mattress elements, without disturbing the characteristics of comfort thereof, nor the homogeneity of their colours. PA1 at least five moulds are located on a circular carrousel, distributed uniformly at 1/5th of the circumference of said carrousel for each and comprising a plurality of hollow recesses opening out in their upper part in a common volume constituting a continuous sole for said cushions and mattresses; PA1 said moulds are automatically transferred, successively and horizontally by said carrousel from a preparation station where a demoulding agent is projected over the whole of their surface, to beneath said head; PA1 said head is displaced by any mechanical means above each mould in a continuous path covering at least all the recesses thereof at a speed which varies depending on the parts of the path and ensuring, on the one hand, for a given flowrate of casting of the product, a desired distribution thereof in each recess, and, on the other hand, a total time of passage over the path less than the maximum time of expansion of the product projected at the beginning of this path; PA1 a cover is closed on each of the moulds, after the end of passage of the head over the path and it is held by any means compensating the effort of the internal expansion pressure of the foam; at the same time, a controlled communication of the internal volume with the outside may be ensured via some vents so that the air can escape without risk of the foam collapsing; the mould thus closed is then transferred automatically by said carrousel towards successive standby stations where it remains for a time at least equal to or preferably greater than that of maturing of the cellular matter obtained and during which the temperature of the mould is maintained in a given range; PA1 said cover is opened, the cushion or mattress element thus constituted is removed and the cleanliness of the mould is checked; the above operations are then recommenced to produce another element from the preparation station which may be the same as the one where the terminated elements are removed or another, distinct station located just afterwards. PA1 the mould-transfer carrousel and the mechanical equipment performing the different operations of displacement of any mobile device, and of casting, recycling, storing the components and any product to be projected, are equipped with physical measurement and position sensors, which are connected to at least one automat for controlling the various equipment concerned; PA1 said automat is automatically and continuously programmed to perform the manufacturing operations concerning at least the displacement and transfer of the mould between each work station, respecting the minimum times imposed between each station, and casting of the product, respecting the maximum time imposed. PA1 on the one hand, to deposit a controllable, regular film over the whole bottom of this mould, thanks in particular to a device described previously, such as a spray pipe parallel to and of the same length as one of the sides of a mould; PA1 and, on the other hand, to project more paint at the level of those parts of the mould corresponding to the hollows of the mattress or cushion elements, which are therefore projecting, and which receive a slightly too full coat at that spot, where the projections then formed are precisely the most stressed; the paint thus participates in the tear strength thereof, even if its thickness is only some microns, which is not possible to obtain with a paint projected afterwards. PA1 after the casting phase which therefore takes between 12 and 25 seconds for example, depending on the foam used, as indicated hereinbefore, and closure of the cover of the mould, then to wait, as the other following two sectors of rotation do not correspond to any work station, of the order of three times 120 seconds less the injection time at the first station of 20 to 30 second, viz. 330 to 340 seconds therefore, which is the precise minimum time necessary for obtaining maturing of the water foam, namely its cross-linking and foaming in the whole volume, then drying until it does not stick; this is therefore effected in three positions of the carrousel, before opening the cover and presenting the mould in its fourth angular position or sector of rotation with respect to that of casting; PA1 after opening of the cover, the manufactured element may then be removed, the quality thereof checked as well as the cleanliness of the mould, during less than half the 120 seconds corresponding to the duration of presence of the mould at this work station; during the remaining time, the demoulding agent may then pass at this same station, which takes only a few seconds and which requires drying of the order of a little more than one minute, therefore in total in accordance with the duration of maintaining the mould corresponding to this station; this demoulding agent may pass at low pressure, of the order of 450 mb, the effect of which is to have a diffusion without ground effect, which thus allows 85% of the product to be deposited in the mould with a minimum fog; PA1 the fifth sector of rotation of the carrousel then corresponds to the position of the station where the water-proof paint is projected when this is desired, knowing that such projection likewise takes only some seconds, but requires drying likewise of the order of a little more than a minute.
Certain of these developments have formed the subject matter of a Patent Application, each for a specific characteristic. Mention may be made for example of French Patent Appln. FR 2 646 772 to Messrs. DUTSCHER and WACKERMAN, published on Nov. 16, 1990 for an "Improved anti-bedsore mattress with longitudinal protection and retaining edges", Appln. FR 2 630 644 to LABORATOIRES ESCARIUS published on Nov. 3, 1989 for an "Anti-bedsore cushion and mattress for medical use", Appln. FR 2 510 377 to the Swedish firm TIMMELE LAMINERING AB published on Feb. 4, 1983 for an "Elastic body covered with a protective layer".
Similarly, mention may be made of European Application EP 114 762 published on Aug. 1, 1984 in the name of the firm SUPPORT SYSTEMS INTERNATIONAL for a "Mattress for therapeutic use, particularly for avoiding the formation of bedsores for a long-term bedridden patient" and which specifically relates to a mattress of waffle-iron type, but of which the foam which constitutes it is constituted by three superposed layers of cellular material having a crush strength increasing from the contact surface of the projections to the sole; and Appln. EP 135 771 published on Apr. 3, 1985 in the name of BAYER AG for a "Cushion whose interior is made of foam and with an air-permeable cover", and which describes a process for manufacturing from a coating material sealed tightly on the foam in which the latter is injected, then a part of the seal is destroyed to render it air-permeable.
All these publications and others therefore describe various possibilities of producing and obtaining either characteristics as set by certain standards such as the French standards mentioned above, or improvements to cushions or mattresses, both in their form and in their composition or protection, but none teaches nor suggests a complete process of manufacture allowing said manufacture to be automatized, at least for obtaining cushions or mattresses by pre-moulding the desired form, which is one of the objects of the present invention. However, such automatization would enable products uniform in their quality to be obtained more reliably, all the more so as foam expanded with chlorofluorocarbide (CFC) type propellant gas are no longer to be used, but water foams which are much more delicate to employ and do not allow variation in the operational conditions; on the other hand, automatization allows a high production capacity in a small space and with minimum manpower.
Thus, the casting or injection of the foam in a mould is often effected manually at the present time, which takes time and does not allow a uniform distribution of the components for producing the foam in the mould, then creating variations in density of the material during expansion thereof once the mould is closed and in the case of water foam, does not allow a good expansion thereof.
Processes and devices proposing a certain automatization are indeed known, such as the one described in U.S. Pat. No. 4,532,093 to Mr. O'MALLEY, for the manufacture of foam-moulded packings, with the aid of an injection head displaced by an automatic mechanical means above a mould to ensure a certain distribution of the foam therein, but the path of the head is very limited and therefore does not allow a real controlled distribution in the whole mould; demoulding is effected thanks to a cover which is placed by hand prior to injection, then removed, which is not practical and slows down operations; the circular carrousel used comprises only two moulding stations and locations; and, furthermore, nothing is specified nor described nor evoked for specifically treating the problems, on the one hand, of moulding objects such as cushions or mattresses composed of adjacent projections such as in the form of frustums of pyramids fast with one common sole and, on the other hand, of the very delicate use of water foams.
In fact, polyurethane foams need a propellant gas to constitute their open cells and, up to the present time, the gases used to that end were alkanes or halogenated, essentially fluorinated hydrocarbons, of which one of the best known is the one bearing the registered Trademark "FREON" of DU PONT DE NEMOURS, and chlorofluorocarbides, called CFCs: however, such gases are at the present time considered noxious and are being progressively prohibited.
A known solution for making open-cell foam is to replace this propellant gas by water which is previously mixed in one of the basic components, for example as described hereinafter, polyol, and which, during the chemical reaction with the other component, which is preferably isocyanate for example, produces an exothermic effect greater than 80.degree. C.; the water is then evaporated and, by secondary chemical reaction, creates carbon dioxide, forming by the gas thus produced the open cells of the foam.
However, such a reaction is slower than with the CFC gases, which requires a longer waiting time for demoulding, during which the expansion pressure produced may be 450 g/cm.sup.2, or equivalent to that of expansion of foam with CFC but, depending on the formulations, can go up to 650 to 750 g/cm.sup.2, viz. double that produced with the CFC gases; the temperature of the mould must also be higher than 15.degree. C. minimum with respect to that necessary with these latter gases, and, on the one hand, cannot be maintained by the sole exothermic reaction of the product itself, on the other hand, must be maintained in a very strict range of 58.degree.to 62.degree. C. and preferably 60.degree. C., on which the quality of the expansion, and therefore of the terminated foam, depend; furthermore, as indicated hereinbefore, the distribution of the product in the mould must be very precise and follow a strictly defined path, which must always be the same, otherwise there are variations in consistency of the foam and heterogeneous cells, both at the level of their diameter and their distribution, which would render the mattresses or cushions thus produced, unusable.
Furthermore, in order to facilitate cleaning and to preserve the mattresses from stains, an external water-proof protection system is often added, which may be a waterproof cover which, inter alia, may hinder deformation of the projections and therefore their efficacy of distributing pressure, and be the cause of noise and friction, and in any case does not completely prevent the foam from being stained; it has been envisaged to add, after manufacture, a waterproof protective film adhering thereto:
The objects of the present invention are therefore to develop a process, and a device for carrying it out, for manufacturing such cushion and mattress elements of supple cellular material, such as polyurethane foam, preferably expanded with water and pre-moulded to the desired form, essentially making it possible: